Sweet Gem Berry is not a fruit so it cannot be placed in the Keg.
Vine/Trellis/Tree Crops are more profitable because they don't require replanting seeds and typically have a faster regrowth rate than the growth rate of the original crop.
|Ancient Fruit||7 Days||1,100g||157.1|
Wheat Seeds: 10g Starfruit Seeds: 400g
After factoring in the cost of seeds, converting Wheat into Beer will net you 165g/day compared to 157.1 from both Ancient Fruit and Starfruit but the biggest difference here is processing time. Wheat takes 4 days to grow but processes in a Keg in 1 day so it will take 4x the amount of crop space to keep up with the Kegs (4:1 crops to kegs -- Keg Ratio) compared to a the simple 1:1 Keg Ratio for Ancient Fruit Wine.
The problem with this is that making Beer becomes a daily tasks instead of leaving Wine to a weekly tasks -- that means less time doing other things in the game.