Ok so quick guide. Did this on android so experience may vary.
1) apple seeds are your friend, use these to stave off hunger and save the rest of the food for mutation.
2) EAT ON THE STEEETS NOT AT THE MACHINE!!!! Got your attention? Reason: game saves when you return to the streets. Get disappointed that your mutation items weren't enough? Quit or let the cops catch you. Game will revert back to before you went to the streets but after you bought/used your items. Not eating at the machine will save you time and prevent you from having to start from scratch if you screw up.
CHEESE METHOD (for those who dont have time): Again did this on android with the game installed (and whatever version it is at the time of this writing) . Get money, return to vending machine, return to streets without spending cash, quit game, reload game, and "Oh look" our hobo heroine (could prolly use some) is now 50% food and 90% thirst. Go get money and repeat. Do this as much as you like till you got the cash and either get the items your aiming for or experiment with the machine.
Edit: Cheese method will revert you to base form. Its mainly intended as a way to get cash without having to spend anything to keep our hobo alive.
on another note,
ADDITIONAL CHEESE: Use the items you wish to transform with. Let cops arrest you. Continue the game once you're back at the main menu. And now your at the mutation you left off with with the items you used restored. Only drawback is if you quit the game you WILL revert to base form regardless of whether or not you go out to the streets and return. (Haven't tried going up another transformation tier yet and having that save)
Cash results (based on my xp)
1$ seeds
5$ 5 seeds
10$ 10 seeds
50$ 50 seeds
100$ 100 seeds, random lower tier food
150$ GUARANTEED DRINK (tested dozens of times, never any seeds)
200$ better food
500$ 500 seeds or much better food
1000$ 1k seeds and even higher food
1K is highest and last tier as I've been made aware.
there's probably ranges i missed but im hoping someone will find the special numbers.
Also see the reply below mine by Crystal to see the spreadsheet they made. Useful info on there.