Oh no! What a pity it's not a Tumbling Tom!

I agree with John that the best thing would be to get it outside pronto where it can reach its full potential. If you clip it, it will sprout some new, stronger growth.

Linda

Poor thing is starved for light and doing everything it can to find some. That is a normal plant response to such artificial growing environment - long lanky weak stems, extra ordinarily long internode lengths, few leaves, compromised circulatory system, etc.. Had it been outside with adequate sun exposure or supplied adequate supplemental lighting inside it would only be 1/3 that size and 5x as productive.

Dave

Dang. Thanks for the info. I will say, however, despite my seemingly neglectful ways, all of the sister tomatoes I put outside are TINY and not nearly as healthy. I realize this could be soil issues, etc.
Although it will hurt, I will clip off the tops and put the poor dear outside. This is my first dabbling in the world of tomato, so it's been fun to watch the transformations. Thanks again for your expertise.

There's no reason to cut off the tops. Just let them grow out the top and cascade back down to the ground.

I do this every years with my plants. Sometimes they'll grow up 6 feet to the top of the cage and back down to the ground.

Put some sort of padding under the wire to cushion the vine.

I'd top it off leaving enough room for some growth of tomatoes, and turn it into as compact a houseplant I gradually could space permitting. Unlike others who want to get it outside, I wouldn't waste my efforts in a perfectly good space outside I could put a better transplant into.

Once a plant develops its stem structure to this extent, I think it's a little late to think about what to do with it since it will be poorly geared for outside life. It has evolved/adapted to the place it's in which is one thing, so I'd just embrace that and see what I could learn about doing houseplant tomatoes more. It would need to be hardened off first if placed outside, and sure it would eventually use the light it needed, but the hardening would take a little more out of an already weak plant. If it gets outside it will be a good while till it possibly could re-invent itself. ...a poster child for the importance of good transplants ;-( But indoors it can be your mad scientist experiment. Don't forget to vibrate any blossoms to assist in pollination.
PC

I'm with PC on this one. At this point, I would lay it down sideways to get light to the entire plant so you don't loose the flowers on top. Good luck and keep us posted.

Yes, good luck, :-)
I guess the unanswered question might be what to do about the "self-watering pot" that has probably become pretty useless by now, if you really aren't up to attempting to slip it out into a larger container for whatever convenience or size restrictions you have inside or out. It's hard to see but is maybe 3 quarts liquid measure? One of the reasons to do some topping besides making it manageable is because more growth = more need for water = more root growth and compacting in there. You won't have any root space to play with, but if you keep it small I think you could have a toy plant giving you a run for the money.

A mad scientist might try putting an empty terracotta pot like one of those you've got herbs in above where the dishes are drying. I'd seal the bottom and have it just sit right on top upright, and I would fill it in the morning and see if I could get it to diffuse out ("wick"), through the bottom and last a day or more. If that didn't work, I'd try a plastic Coke bottle with a few of the tiniest pin-pricks sitting on top contacting the growing medium/soil, (and keep the screw cap for that). Don't know if that would be exciting for you but I think it would be a great learning project about water movement if you wanted to play around with it in the comfort of your kitchen.
PC (just mulling about)

Agree with PC too. As I indicated above the poor thing is likely beyond salvaging at this point and its internal systems are so compromised it likely wouldn't survive outside now. If you want to try to save it by cutting it back just to see what happens you could try rooting a small cutting from it and then harden off that cutting and plant it outside. If the long term goal is growing tomatoes indoors then there is much good into on the lighting set-ups needed to do it successfully over on the Growing Under Lights forum here.

Dave

I'm impressed. I don't know; looks look you have one very attractive houseplant. I'd go with that and just let it be, as others above have advised. Tomatoes are too easy, cheap and fast to attempt to grow one that is already at a disadvantage outside for fruit.

I never leave my seeds indoors long enough to get etiolated but have seen others'. This specimen, however, is quite attractive. I might try this in my living room next year, haha!