I normally don't use sinking funds, because I'm not saving for anything in particular at the moment and the only erratic expenses I have are car and renters insurance. Current cost is $369 Apr/Oct for car, and $139 Aug for renters. These will go up a little, because I've just increased my liability coverage. I paid the prorated difference yesterday - $24 (money well spent).
Usually I just cover this in the ordinary monthly cash flow when they come up, lowering or skipping savings for the month. But this year I am really focused on retirement savings, and I want those contributions to be consistent month to month, so I think I do a sinking fund for this.
Allowing $800/150 for ball park amounts, I can put in about $80 a month. That won't quite have it covered for the April payment, but I can make up the difference from my tax refund or just let it go and pull that much from ordinary cash flow.
I will put this in my emergency fund account. .I am holding my emergency fund for the present at four months, and I have that now with my deposit a few days ago. Anything over that amount will be construed as sinking funds, so interest, such as it is, will also be rolled into the sinking funds. I'll look at the accounts again. I can probably squeeze a little more into it for January.