I started playing 3...g6 vs. the Spanish about 10-15 years ago and have been pleased that in some lines I can get sharp play quickly with either 4. c3 f5!? or 4. 0-0 Bg7  5. c3 d5?! 5...a6 instead is what grandmasters prefer, here though is a 10-minute game of mine from this morning.  I lost but it was enjoyable, and shows some of the themes of incorporating an early ...d5 into defending the Spanish with ...g6

The Barnes system. Occasionaly played by Smyslov and Spassky. After 3...,g6, i play simply 4.d4. I'm not very happy when my opponent play 3...,g6 and yes, that's a sharper line (for me!).

4 d4 exd4, 5 Bg5! is hard to answer.

4 d4 Nxd4, 5 Nxd4 exd4, 6 Qxd4 Qf6, 7 e5! Qb6, 8 Qxb6 axb6, 9 Nc3 gives White a lead in development.

4. d4 exd4  5. Bg5 is not at all especially hard to answer, simply 5...f6 and if 6. Bh4?! Bc5 holding the pawn for a while, and if White castles too early, a kingside pawn storm with ...h5 and ...g5.  The key for Black is to forego the fianchetto that 3...g6 seemed to prepare, and yet the move still has a use: keeping White's queen out of h5 after a possible Nxd4 by White; 6...Bc5 makes that re-capture difficult for White though a gambit style follow up with c3 may be in order

4. d4 exd4  5. Bg5 f6  6. Bf4 is a better try for White

I'm not a great chess Player, but for my style, i play 6.Fh4 and give a pawn (c2-c3) for the initiative...