^^^^ well when you are taking something like helladrol or any AAS that creates an anabolic and androgenic environment in the body you can get away with eating slop and still manage to gain muscle as long as you work out. however you wouldn't be maximizing the cycle's potential.
as for your question on vending machine, I suppose I would pick whatever had the least amount of bad fat, salt and sugar. potato chips have tons of oil/salt, and pop tarts have tons of sugar and i'm sure salt. I would encourage you to take one of those small coolers and take some fruit with you, carrots/celery.. a sandwich, even a hardboiled egg. living in cali i'm sure you have farmers markets everywhere with fresh in season produce, take advantage.
here is an ingredient list for pop tarts i found online.. this is indicative of anything you get out of a vending machine. it is can sit in a vending machine for months and still be okay to eat you know it can't be good. i highlighted the things that are responsible for why we have diabetes and obesity epidemic in the country
ENRICHED FLOUR (WHEAT FLOUR, NIACINAMIDE, REDUCED IRON, THIAMIN MONONITRATE [VITAMIN B1], RIBOFLAVIN [VITAMIN B2], FOLIC ACID), SUGAR, DEXTROSE, VEGETABLE OIL (SOYBEAN, PALM, COTTONSEED AND/OR HYDROGENATED COTTONSEED OIL† WITH TBHQ AND CITRIC ACID FOR FRESHNESS), CORN SYRUP, WHEY, CRACKER MEAL, HIGH FRUCTOSE CORN SYRUP, COCOA, CONTAINS TWO PERCENT OR LESS OF CORNSTARCH, COCOA PROCESSED WITH ALKALI, SALT, LEAVENING (BAKING SODA, SODIUM ACID PYROPHOSPHATE, MONOCALCIUM PHOSPHATE), MODIFIED CORN STARCH, MONO- AND DIGLYCERIDES, SODIUM STEAROYL LACTYLATE, GELATIN, DRIED EGG WHITES, DATEM, PARTIALLY HYDROGENATED SOYBEAN OIL†, MODIFIED WHEAT STARCH, XANTHAN GUM, NATURAL VANILLA FLAVOR, CARAMEL COLOR, SOY LECITHIN, CALCIUM PHOSPHATE, COLOR ADDED, NIACINAMIDE, REDUCED IRON, VITAMIN A PALMITATE, PYRIDOXINE HYDROCHLORIDE (VITAMIN B6), RIBOFLAVIN (VITAMIN B2), THIAMIN HYDROCHLORIDE (VITAMIN B1), FOLIC ACID