The best way to get profits from farming vegetables is to cook them or make food from them, but if you want to just make some cash without waiting too much, then your best course of action would be to farm:
Wheat --> Tomato --> Cucumber --> Hops --> Heart Flower
This way you can maximize the amount of money you make with each harvest. You can see the money it costs, money you get from each product and the money you get from a full harvest in the chart below.

Of course you can also maximize the amount of profit you get from selling fruits as well. The best course of action for only fruits would be:
Blueberries --> Strawberry
Strawberry wins the award of being the most profitable plant overall which will be also mentioned in the next chapter by a huge margin of 37 money profit. You can see the exact values on the chart below. The collumns from the left to right specifying the fruit, how much it costs to plant, how much 1 of it sells for and how much a full harvest sells for.

If we combine and compare our results from the fruits and the vegetables, strawberry naturally comes on top. I can't make a specific planting route for the fruits and vegetables combined because I don't remember the order in which you unlock them but if you compared them, it would look like this:
Strawberry > Heart Flower > Hops > Blueberry > Cucumber > Tomato > Wheat
So in conclusion the best thing to do is to start planting strawberries when you first unlock them. I believe this could change in future balance updates but until then, strawberries are the best way to profit from selling only crops. But always remember that your profits could increase tenfold by settings up rows of ovens and stonemills etc. to make extra products from crops and selling them by themselves or completing the quests. With that, I'll end this guide and leave you on your way to getting the 100k coins achievement. Good luck on your journey!