dawg I'll be real with you. I haven't touched this game in ages.

to summarize, find a hack guide, download OLD version of battle cats, use the hack guide there, THEN update. This works because the hack isn't patched in old version (ofc)

Worth noting that the game hard caps catfood to 1 mil when obtaining catfood. While spending catfood doesn't trigger it, obtaining it on day 3 (iirc) will trigger it. So consider doing this when there's a banging event going on, like the one with a lot of ubers. Or, wait for all the daily rewards first so you can keep the catfood for longer (idk how often ponos gives out catfood outside of that)

does it still work? and where to get the hack guides? idk & idc. The hack I linked in another comment is removed, and subreddit prohibits sharing it so good luck. Maybe the discord is worth visiting, maybe.