every short option got +theta.. it increases ATM and decreases OTM/ITM, increases with less DTE and decreases with more DTE.
Considering this, the highest decay would be an ATM option about to expire. An ITM/OTM LEAP would have the least decay, so totally the opposite of what you are looking for.
On top of this, the decay accelerates in the period between 40 and 20 DTE, so a short straddle or a narrow short strangle within this time frame could be a reasonable source of +theta.
The problem is that this is a naked short position, you get massive gamma/vega risk. Could work in the period after a price shock, when you profit from time decay, volatility contraction and a consolidation/accumulation pattern in the underlying.
You must be sure however that the event that triggered the spike is a "one-off" mean reverting event where after the initial shock it's business as usual. (For instance, some industrial incident happening, News that turn out to be fake, some CEO tweeting nonsense etc.). In case of an unfolding situation that involves a paradigm shift (FED decision, etc.) I would be much more careful.